Temperature controlling device



June 4, 1935. v; o c 2,003,956

TEMPERATURE CONTROLLING DEVICE Filed. March 31, 1933 INVENTOR ll L. RON C BY RNEY Patented June 4, 1935 TEIVHERATURE CONTROLLING DEVICE Victor L. Ronci, Brooklyn, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 31, 1933, Serial No. 663,766

12 Claims.

This invention relates to temperature controlling devices and more particularly to thermal contact switches or thermostats.

In the usual thermostat one or more contacts are sealed through the wall of the vitreous container and are exposed in the fine bore capillary to an expansible conducting body such as mercury, in order to establish an electrical circuit of which the expansible body is a part. Serious difflculties are encountered if the contact or contacts project into the capillary so as to reduce the cross-section thereof. Under such a condition adhesion of mercury to the contacts results in breaking the column of fluid and rendering the device inoperative. Another difliculty is the sealing of the contacts in the glass. This operation requires a skilled worker in order to insure alignment of sections of the capillary during sealing and accurate positioning of the contacts in order to obtain a required exposure of the contacts in the capillary bore. These difliculties increase the cost of thermostats due to the large loss in time and waste material.

An object of this invention is to facilitate the 26 manufacture of thermostats whereby the contacts may be sealed in by a machine.

Another object of the invention is to insure adequate contact surface with the mercury in the capillary bore without causing blocking by 30 adhesion.

In accordance with this invention a vitreous tube having an axial capillary bore communicating with a chamber or reservoir at one end containing an expansible conducting fluid such as mercury and at the other end terminating in an expansion chamber, is cut or severed transversely at a desired position in the capillary bore and a perforated fiat contact sealed between the severed sections of the capillary with the perforation in the contact offset with respect to the axes of the capillary sections. A leading-in wire is also sealed in the end of the reservoir and is continuously in contact with the body of merucry therein. Expansion of the mercury due to elevatlng temperatures will cause the mercury to ascend in the capillary portion and conductively close an electrical circuit which is connected to the contacts of the thermostat.

Since the capillary portion of the thermostat must be severedin'order to insert and seal the contact therein, visual precision must be practised by a highly skilled glass artisan in order to attain accurate alignment of the capillary bore of the two sections of the vitreous tube while insurlng adequate protrusion of the contact into the capillary bore so that the mercury will engage the contact. In accordance with this invention these difiiculties are overcome by a meth- 0d of assembly which can be accomplished by machine without the aid of skilled workers. This 5 method consists in arranging the two sections of the cut capillary tube and the perforated contact between the sections and threading a guide member through the capillary bore and contact to maintain these details in position. This assembly is inserted in a revolving head of a sealing machine and the contact sealed between the sections of the capillary tubing. After cooling the guide member is removed, the mercury injected and the tubing sealed off to complete the thermostat.

The perforated contact insures positive contact surface in the capillary bore since the probability range of obtaining adequate contact is increased by the circular edge of the contact member. If the glass flows over the edge of the contact at certain points during the sealing process the probability of the glass flowing to entirely embed the contact is extremely remote.

The various features of the invention will be more clearly understood from the following detailed description in connection with the accompanying drawing:

Fig. l is a perspective view of a thermal element made in accordance with this invention showing the assembly of the contact membe in the capillary portion; I

Fig. 2 shows in perspective the positions of the separate parts of the thermal element prior to assembly;

Fig. 3 is a vertical cross-sectional view of the parts shown in Fig. 2 illustrating the alignment of the sections of the casing and the contact with the aid of a guide member preparatory to sealing the contact between the sections;

Fig. 4 is an enlarged cross-sectional view on the line 4-4 of Fig. 3 showing an exaggerated relation of the sizes of the capillary bore and the aperture in the contact; and

Fig. 5 illustrates a modification of the thermalelement of this invention in cross-section with a number of contacts sealed in the capillary section.

Referring to the drawing, the thermostat shown in Fig. 1 comprises a length of common whiteback capillary tubing forming the receptacle or casing l0 having a reservoir ll containing an expansion fluid such as mercury l2. The closed end of the reservoir is provided with a leading-in Wire l3 which is in contact with the mercury body in the reservoir and forms one terminal for establishing an electrical circuit. The reservoir ll communicates with a fine bore capillary H which terminates in an expansion chamber I located at the opposite end of the device.

The contact I6 is sealed in the capillary I4 at a predetermined point and forms a second terminal for an electrical circuit. The location of the contact it depends upon the temperature at which the operation of the thermostat is desired. For instance, if the thermostat is to be operated when a temperature of 60 F. is attained, the contact I6 is sealed in the capillary at a point determined by the size of the capillary bore, length of the bore, the area of the reservoir and the amount of liquid contained in the reservoir. Consequently when the thermostat is within a heated enclosure, the gradual increase in temperature therein causes mercury to expand and rise in the capillary bore until at the temperature of 60 F., the mercury comes into engagement with the contact l6 and the electrical circuit is completed to operate a suitable relay or signal device.

The contact IS in accordance with this invention is a metallic ribbon, preferably platinum, having an aperture l1 slightly larger than the capillary bore and when sealed in the glass bore of the capillary portion presents an extended surface of arcuate form to the column of mercury entering the capillary bore. This form of contact insures an adequate surface because the probability of the glass flowing over the entire edge of the aperture in the contact during the sealing-in process is remote. Furthermore, the edge of the contact exposed in the capillary bore is not of sumcient depth to separate the column of mercury. This difilculty is quite prevalent with the usual wire type of contact.

The method of making thermostats and sealing-in the contact will now be described with reference to Figs. 2 and 3. A length of common spirit white-back capillary tubing having an outside diameter of .195 inch and inside diameter of .007 inch is heated in a glass-blowers flame and an expansion chamber I5 is blown adjacent one end thereof. Then the other end of the tubing is heated in a similar manner to form the reservoir ll.

Intermediate the reservoir and the expansion chamber is a definite length of capillary bore ll in which the contact I! is to be positioned to be engaged by the mercury column. In order to make the seal, it is necessary to separate the capillary tubing and this is conveniently done by breaking the tubing sharply at a point at which it is desired to place the contact. The breaking of the tubing avoids variations of the contour and diameter of the capillary bore since it is obvious any other method of separation may change the shape of the bore. After the capillary tubing is separated, a guide member or wire l0, such as a molybdenum wire having a diameter of .005 inch is threaded through the sections having the expansion chamber ii, the wire being inserted through the end of the tubing adjacent the chamber i5 and then extending through the bore N. The guide wire is then inserted through the aperture I! in the ribbon contact It. The diameter of the aperture is, for example, .012 inch and the thickness of the contact may be one mil. The guide wire is finally threaded through the other section of capillary tubing, first entering the bore I4 and then extending through the open reservoir ll.

The assembled details are now in position to be placed in a. rotary head of a glass sealing machine, provision being made to hold the sections of tubing against individual movement and the ends of the guide wire being held under tension to insure an accurate alignment of the capillary sections and the contact on the guide rod. After the details are placed in position in the head of the machine the two sections of tubing are adjusted to align the white backing in the tubing and to fit the two faces of the broken tubing in order that the glass grain may be properly aligned. The contact is positioned in the center oi the white backing intermediate the longitudinal edges thereof and the end of the contact projecting from the side of the capillary tubing is tensioned slightly to cause the inner edge of the aperture ll away from the point of applying the tension to engage the circular surface of the guide wire 18. The tension applied to the contact, however, is not so great as to misalign the guide wire. This results in the aperture in the contact being eccentrically arranged with respect to the capillary bore and the wire l8.

Now the details are prepared for sealing the contact between the glass sections of tubing. The head of the machine is rotated in a well-known manner and a single stationary burner fiame on the machine is directed toward the position of the break between the tubing. The burner flame is adjusted to a fine point in order to limit the area of glass which is subjected to heating to form the seal. The flame applied to the rotating assembly causes the glass to soften and weld together at the break and hermetically seal the contact in place. During the sealing of the contact in the glass, a diatomic gas, such as nitrogen, is continually passed through the capillary tubing to prevent oxidation of the molybdenum guide wire and also to prevent the collapse of the glass.

After the sealing operation is completed, the gu de wire is removed and this is eflectively accomplished by stretching the wire I! to the breaking point and the two pieces of wire are drawn out of the capillary bore. The breaking of the guide wire avoids kinks or bends in the wire which might score the capillary bore.

When the gu de wire is removed from the capillary tubing the seal is annealed by heating to a temperature of 465 C. for one half hour by a soft flame, such as a flame without air or gas pressure, and then cooled for two hours. The heating and cooling produce a proper annealing treatment to offset cracking of the glass in subsequent operations. This annealing treatment also removes any molybdenum oxide which may have adhered to, the wall of the capillary bore. The capillary tubing is removed from the machine and cleaned thoroughly in an acid bath and then in a distilled water bath to remove any particles of foreign matter from the capillary tubing. After the cleaning operation, the end of the tubing containing the reservoir is closed by forming the glass on the end of the reservoir and piercing the closure by forming a central aperture to receive a wire contact l3 which is hermetically sealed in position as shown in Fig. 1.

The completion of the sealing operation of the contact in the capillary tubing prepares the thermostat for the filling operation. The capillary tubing is attached to an exhausting system and heated in an oven to remove water vapor and highly evacuated to remove contaminating vapors or air in the vessel.

After the device is exhausted, a regulated quantity of mercury is injected into the capillary bore and substantially fills thereservoir II. It will'be evident that the mercury is mechanically and electrically in contact with the terminal l3 in the end of the reservoir. Prior to sealing of! the end of the thermostat from the exhausting system an inert gas, such as argon, is injected into the capillary bore, at a pressure equal to atmospheric. The purpose of the gas is to prevent the separation of the column of mercury since the head pressure of gas insures the mercury being maintained in a continuous column. However, when the column of mercury is elevated in the capillary bore, the increased pressure of the gas is negligible and does not cause irregular action of the mercury nor cause an incorrect indication of temperature.

It will be apparent from Fig. 4 that the arcuate surface 20 exposed in the capillary bore of the tubing presents an extended surface to the rising column of mercury and does not project too far into the capillary bore to cause separation of the column of mercury. It will be evident that the arcuate surface of the contact in the capillary bore precludes the possibility of glass, during the sealing operation, completely flowing over all the edge of the contact exposed in the capillary and consequently if some of the edge is entirely embedded by the glass there is still sufllcient surface exposed in the capillary to form an efficient contact.

It is of course understood that variations of the diameter of the capillary bore in the tubing will necessitate a change in the diameter of the aperture in the contact I6. The invention may also be practised in a thermostat in which multiple contacts are arranged in the capillary bore to accommodate the thermostat to a wider range of control. For instance, as shown in Fig. 5 the three contacts 2|, 22 and 23 which are similar to the contact l6 described in the other figures may be arranged at elevated positions in the capillary tubing and sealed-in simultaneously by the method described herein. It is also apparent that the shape of the aperture in the contact need not necessarily be circular, but may assume other forms to carry out the object of this invention. Furthermore, various other features of the invention may be modified without changing the scope of the invention as defined in the appended claims.

What is claimed is:

1. A temperature controlling device comprising a vitreous vessel having a capillary bore and a reservoir at one end thereof, a terminal extending into said reservoir, a body of expansible conducting material in said reservoir, and a metallic contact having a perforated portion eccentric with respect to said bore sealed through the wall of said vessel, the perforated edge of said contact extending into said capillary bore to the extent of at least a 90 degree arc.

2. A temperature controlling device comprising a vitreous vessel having a capillary bore and a reservoir at one end thereof, a terminal extending into said reservoir, a body of expansible conducting material in said reservoir, and a thin flat metallic contact having a perforation therein, a continuous portion of the perforated edge extending into said bore and the remaining edge of the perforation and the edges of the contact being embedded in said vessel.

3. A temperature controlling device comprising a vitreous vessel having a capillary bore and a reservoir at one end thereof, a terminal extending into said reservoir, a body of expansible conducting material in said reservoir, and a metallic contact having an annular portion sealed in the wall of said vessel, the axis of said annular portion beingeccentric with respect to the axis of said capillary bore. 4. A temperature controlling device comprising a vitreous vessel having a capillary'bore and'a reservoir at one end thereof, a terminal extending into said reservoir, a body of expansible conducting material in said reservoir, a contact ex-'- tending through the wall of said vessel and having a portion exposed in said capillary bore, and a filling of inert gas in said capillary bore.

5. A temperature controlling device comprising a vitreous vessel having a capillary bore and a reservoir at one end thereof, a terminal extending into said reservoir, a body of mercury in said reservoir, a metallic contact extending into said vessel and exposed to said mercury in the capillary bore, and a filling of argon at atmospheric pressure in said vessel.

6. The method of sealing a metallic contact in a capillary vitreous vessel which comprises, separating said vessel transversely in the vicinity of said capillary, piercing a contact to provide an aperture substantially corresponding to the diameter of said capillary, assembling the separated portions of the vessel with the apertured contact therebetween on a guide member, sealing said contact in said separated portions, and removing said guide member.

7. The method of sealing a metallic contact in a capillary vessel which comprises, separating said vessel transversely in the vicinity of said capillary, forming an aperture in the contact sub-* stantially corresponding to the diameter of the capillary, assembling the separated portions of the vessel with the apertured contact therebetween on a guide member, tensioning said contact to locate the aperture therein eccentric with respect to the capillary, sealing the contact in the vessel, and removing said guide member.

8. The method of sealing a metallic contact in a capillary vessel which comprises, separating said vessel transversely in the vicinity of the capillary, forming an aperture in the contact substantially corresponding to the diameter of the capillary, assembling the separated portions of the vessel with the apertured contact therebetween on a guide member, sealing the contact in the vessel, stretching the guide member to the breaking point, and removing the parts of the member from opposite ends of the capillary.

9. The method of sealing a metallic contact in a capillary vessel which comprises, separating said vessel transversely in the vicinity of said capillary, forming an aperture in the contact substantially corresponding to the diameter of the capillary, assembling the separated portions of the vessel with the apertured contact therebetween on a guide member, sealing said contact in the separated portions of the vessel, and injecting a flow of a non-oxidizing gas in the capillary during the sealing operation.

10. The method of sealing a metallic contact in a capillary vessel which comprises, separating said vessel transversely in the vicinity of said capillary, forming an aperture in the contact substantially corresponding to the diameter of the capillary, assembling the separated portions of the vessel with the apertured contact therebetween on a guide member, sealing the contact in the vessel, passing nitrogen through the capassembling the separated portions of the vesselwith the apertured contact therebetween on a guide member, sealing the contact in the vessel, passing nitrogen through the capillary during the sealing operation, removing the guide member, annealing the seal, evacuating the vessel, filling the vessel with an expansible liquid, injecting argon gas after the liquid filling, and finally sealing said vessel.

12. A temperature controlling device comprising a vitreous vessel having a capillary bore and a reservoir at one end thereoi','a body 0! expansihle liquid in said reservoir, and an eccentric metallic contact having a perforation with a continuous edge sealed through the wall of said vessel, said contact having an arcuate portion extending into said capillary bore to the extent of at least a 90 degree arc.

VICTOR L. RONCI. 

